I am switching to a d flip flop and some and/nand gates.
I’ll bet I have not purchased a gate chip for >20 years.
This way I will only have to do an output from the Pi ever 193 cycles.
I can count clocks and then assert the correct output for that one cycle.
The rest of the time the D flip flop will be just repeating the GPS.
Once I get this working I am going back to the arduino to see if it is fast
enough to take the place of the PI.
Or, maybe I will go D flip flop crazy and do the whole thing in a finite state
machine...
From: Bill Prince
Sent: Thursday, February 22, 2018 4:58 PM
To: Motorola III
Subject: Re: [AFMUG] OT Raspberry PI
Pretty sure you need RTOS to accomplish this.That will get pretty close to
bare metal.
-bp
--
bp
part15sbs{at}gmail{dot}com
On Thu, Feb 22, 2018 at 3:36 PM, <ch...@wbmfg.com> wrote:
Had the command syntax wrong.
But got nice to work. Have to sudo if you use negative nice numbers.
It made zero difference in my jitter. I went from 19 to –20 on nice and no
change.
From: ch...@wbmfg.com
Sent: Thursday, February 22, 2018 4:29 PM
To: af@afmug.com
Subject: Re: [AFMUG] OT Raspberry PI
The problem is there is a crap ton of stuff out there that needs network
sync. And it all has a T1 as an input.
But most T1 trunking circuits are getting replaced with SIP.
So, I am building a cheap and dirty T1 signal generator that is GPS and
rhubidium referenced. The hard part is easy. The easy part should be easy but
all the T1 framing chips that used to exist no longer exist.
The ones that are out there have massive CPU interfaces and tons of registers
that need to get set to get them fired up and running....
Where is Exar when you need them....
From: Adam Moffett
Sent: Thursday, February 22, 2018 4:21 PM
To: af@afmug.com
Subject: Re: [AFMUG] OT Raspberry PI
Tell whoever's got the T1 that 1967 is way behind us and get a new interface.
Problem eliminated LOL
------ Original Message ------
From: ch...@wbmfg.com
To: af@afmug.com
Sent: 2/22/2018 6:16:45 PM
Subject: Re: [AFMUG] OT Raspberry PI
I have to generate an alternate mark inversion signal on 1.544 MHz with
every 193rd bit following a t1 framing sequence.
Sure wish a 555 could do that.
From: Dave
Sent: Thursday, February 22, 2018 4:10 PM
To: af@afmug.com
Subject: Re: [AFMUG] OT Raspberry PI
Find a 555 timer ... I used many in the olden day when radioshacks were
king LOL!
On 02/22/2018 05:05 PM, ch...@wbmfg.com wrote:
I am thinking of using some shift registers instead of using the PI
output directly as the timing signal.
Use the PI to load them.
I love me some hardware design anyhow....
From: Colin Stanners
Sent: Thursday, February 22, 2018 3:59 PM
To: af@afmug.com
Subject: Re: [AFMUG] OT Raspberry PI
Other than setting the process priority, you may need a custom kernel.
See
https://medium.com/@metebalci/latency-of-raspberry-pi-3-on-standard-and-real-time-linux-4-9-kernel-2d9c20704495
On Feb 22, 2018 4:48 PM, <ch...@wbmfg.com> wrote:
Anyone know how to get my program to run on bare metal?
Or at the very least tell Linux that my program is the most important
thing in the world and service it above all other things.
I am trying to create a timing signal with the Pi. It is doing it but
the jitter is pretty bad.
I have researched trying to use an interrupt but there is a pretty low
limit on how many times per second you can fire a hardware interrupt.
Too low for my application.
--
